1. Field of the Invention
This invention relates to a frequency converter circuit which has a primary circuit with a primary winding of a transformer which is connected to a DC voltage source through an electronic switch and a secondary circuit wherein the secondary winding is conducted through a rectifier to a storage capacitor which is arranged at a first feed output. A pulse width modulator controls the electronic switch and is connected to a controller and at least one additional secondary circuit is connected to additional secondary windings of the transformer so as to generate a voltage that is lower than the output voltage of the one secondary circuit and each of the additional secondary circuits contain a rectifier diode and a switch controllable by controllers in a series arm and contain free-wheeling diodes in a shunt arm such that the two diodes are polarized so that they can be connected together and to terminals and wherein a LC element is connected to the free-wheeling diode and the capacitor of such LC element forms a further output of the frequency converter circuit. The frequency converter circuit contains a controller that directly or indirectly regulates the output voltage of the secondary circuit. An actual value which is supplied to the controller can thus be the output voltage of the secondary circuit or the output voltage of an auxiliary circuit which simulates the secondary circuit which is connected to an auxiliary winding of the transformer. EMF control is obtained by the use of the output voltage of the auxiliary circuit which is proportional to the no-load voltage. The EMF control has the advantage that the current separation of the secondary circuit in the controller is accomplished using the transformer.
2. Description of the Prior Art
Power supply devices which are used to supply a plurality of output voltage that differ in amplitudes and polarity and with low variations between no-load and full load are required for feeding communication transmission systems. In many instances such power supply devices are formed as flow frequency converters or blocking frequency converters according to known principles.
The article by H. Gummhalter entitled "Stromversorgungssysteme der Kommunikationstechnik", Part 1, Fundamentals, Pages 215-223, Siemens AG 1983 disclose how to form autoconverters as single-ended flow converters or as single-ended blocking frequency converters.
In the known single-ended flow frequency converter, the energy acceptance at the primary coincides time-wise with the energy output at the secondary side.
Primary current flows during the conductive phase of the transistor. Since the primary winding and the secondary winding are wound in the same direction, current will flow secondarily to the load through the conductive diode and the inductor at the same time such that a smoothing capacitor in the secondary circuit is charged. The smoothing inductor connected in the secondary circuit stores energy during this time. The current supply into the secondary circuit is interrupted during the inhibit phase of the switching transistor. The inductor supplies output energy to the load through the free-wheeling diode until the end of the period and until the smoothing capacitor has been discharged. A device for regulation and control switches the transistor so that it is conductive during a period as long as the output DC voltage remains constant with fluctuating input voltage and/or variable load. The demagnitization winding is used so that the transformer does not go into saturation. During the inhibit phase of the switching transistor current flows in the reverse direction through a diode connected in series with the demagnitization winding and through the demagnitization winding and, thus, prepares the transformer for the next conductive phase.
In the known single-ended blocking frequency converter energy pick-up and energy emission are offset in time. During the conductive phase of the switching transistor, current flows only through the primary winding of the transformer because the primary and secondary windings are wound in opposite directions. In the conductive phase of the switching transformer, the diode in the output circuit is polarized in a non-conducting direction so that current does not flow through the secondary winding. The load is supplied only from a smoothing capacitor in the output circuit.
The polarity of the voltage at the transformer reverses in direction during the inhibit phase of the switching transistor. The diode in the output circuit then becomes conductive. The energy stored in the transformer during the conductive phase is supplied to the load. The smoothing capacitor is recharged at the same time.
Autoconverters which allow a plurality of output voltages to be generated can be provided with an EMF control and can be provided with a re-adjustment means and at least part of the output circuits. In the known EMF control circuits, the output voltage of an auxiliary winding of the transformer is used as the actual value and is compared to the rated value of a shared rated value generator in the regulation and control. The wiring of the auxiliary winding is the same as in the secondary windings for the output voltages.